Rotary fastener tool driving attachment for portable power tools



Dec. 6, 1955 H .\SHO

ET AL ROTARY A TE E TOOL IVING ATTACHMENT LE ER TOOLS R PORTAB Filed Nov. 19525 I7 50 IO 52 INVENTOR. HAROLD 0. SHORT BY GLENN c. WILHIDE ATTORNEY United States Patent 6 ROTARY FASTENER TOOL DRIVING ATTACH- MENT FOR PORTABLE POWER TOQ LS Harold 0. Short and Glenn- C. Wilhide, Towson, Md.,.

The-present invention'relates'to a rotary fastener tool driving unit or attachment'for use in connection with portable power tools, and more particularly to a clutch type driving unit adapted for attachment to,-or chucking in, an electric drill, which unit further-includes a rotary fastener'driving tool.

Fo'r theapplication ofelectric motor power in driving or running down and tightening fastener elements such as woodscrews, metal screws, bolts and the like, apt rotary tools such as socket wrench'or screw driver bits may be connected to the motor by a positive fixed mechanical coupling"'for example the driving tool may be chucked in "an" electric drill for driving the fasteners. However,

due'to the speed of rotation-ofthe'tool; even with the ordinarytypes of reduction-gearing often found in port abletools'ysome difficulty is encountered in achieving a timely removal of applied torquewhen the fastener has been driven'to desired tightness or to seated position. Thus, fonexample, when a'screw has been'driven to full depthor-full seated position, as a practical matter it is nigh impossible to withdraw the driving bit from a screw to avoid damage to tool, screw or work; or alternatively to shut oh the motor at some time prior 'to' seating and depend upon inertia of the moving parts to drive the screw to desired position or tightness. Of course should the tool not be withdrawn in time from the screw or other fastener or the power be not-cut off, the fastener or bit maybe sheared, the tool engaging areas deformed and torn by the bit, or threads on work andfastener stripped. To overcome these difiiculties, a variety of clutch type driving mechanisms have'appeared in the'prior art directed to providing-a'disengageableor slip driving connectionbe tweenthe motor shaft and the fastener drivingtool.

Such devices, however, have labored under various dis-' advantages of insensitive control, complexity of mechanism or structure, bulk in size, and inconvenient weight" The unit here presented is rugged, compact and light, simple in structure and assembly," and in operation for the purposes intended. An object of the presentinvention is the provision of a simple 'clutch' type unit which is readily applied to or chucked in the usual type portable electric hand tools such as electric'drills and the "like.

Another'object is the provision ofaclutch type driving unit attachment for rotary hand toolswherein varioustool bits such as-screw driver bits or wrench bits may be readily chucked or interchanged. A further object is the provision of such a driving unit having a casing or housing of a non-rotatable type which may be held in the hand to direct and steady the application of a tool bit to its work. A still further object of the invention is the provision of a driving attachment unit of the clutch typefor use with portable hand tools, wherein the maximum torque or rotational force applied to the work may be sensed or controlled by the manual force or pressure of the operator necessarily directed axially of the rotating tool shaft to the fastener to maintain the elements of the unit in driving, position and relation with each other and the fastener.

Patented Dec. 6, 1955 nalledin member 11 a-tool or' bit chucking-spindle 13 coaxial with spindle-12 and adapted to-removably receive or chuck a-rotary'tool bit 14' such as a screwdriver or" socket wrench bit, the 'two' spindle elements having op posed headed portions 12a and13a of such shapeas to' provide cooperating clutch faces of aclutch mechanism" and a clutch spring 15 interposed in coaxial alignmentbe' tweenthe spindle-elements to bias the clutchfaces'oufi of engagement.

The 'hollow housing member =10 is preferably or generally of cylindrical exterior form andis here shownwith longitudinal exterior-grooves '16providing "manual purchase thereon. The shank -or shaftportion of-spindle" 12 projects through and is journalledin-an-axial bored? in the-reduced end portion of the housing member'lli being held against axial displacement by the head' p'or--'-- tion-12a bearing -on or outwardly ==againsf 'the housing member, and by a thrust washer 18 bearing'against the" outer end'of the housing'member'and securedin position-"- by a snap or splitting 19"or the like engaged in a Circum= ferential groove in the projecting part'of the spindle To reduce frictionb'etween the head of thespindle and the housing, the end .'wall bearing area of the latter is relieved and reduced by a groove 20 concentric with the-bore 173" The cylindrical body portion of nose piece 11 is, as by press fitting, fixed in the counter bore 22 at the open end" of the hollow housing member, and'the counter bore shoulder 23 provides a stop limiting the assemblyin'ser-" tion of the nose piece 11 to determinea'selectedspacingbetween the flat nose-piece 'inner' end and the opposite" parallel inner surface of the housing. This'structure facilitates assembly'of the unit with proper'clearancesthe hollow clutch space. The shank or shaft portion ef-the driven or tool spindle 13 is journalled in an axial bore'25 in the cylindrical nose'piece in rotatable and slidable manner, theouter end of the bore-being'counte'rbored at 26 a sufiicient depth to ensure clearance relatively to certain chucking elements of the driven spindle," even upon inward slidingof the latter for clutch engagement? The '-two spindleelements -12 andll3 "are ofgenerally similar external form, the centered disk like head portions 12a-and 13a having on the opposed head faces an annular? formation including a series of equi-spaced like projecting" clutch teeth 27 as may be seen in detail=Fig.'2. These teeth, since providing' cooperating' clutching or inter-em gagingprojections, are of identical shape,-spacingand"" location'on the two opposed spindle facesyand fdrrota tion or driving of the tool-in either direction, are'eachf'" symmetrical -to a radial plane "with generated engaging" faces 27a on-either side each face 'at its center being 30 from a line parallel to the axis. The fiat radial toothend may be shorter'thanthe radial ba'sefiat between' teethi that-is, the *tooth-i spacing isgreater than-tooth 'widthto allow some rotational lost motion in engaged axial position.

The driven spindle 13 is axially bored inwardly from the clutch face end a distance sufiicient to form a spring well 29 with fiared mouth receiving a major portion of the length of the helical clutch disengaging spring 15,

while the driving spindle has a centered countersunk or conical recess 30 adapted to receive the pointed head of a spring centering piece 31 with its shank inserted or fitted into the end of the spring and extending slightly into the well when the clutch mechanism is disengaged. The spring well in the driven spindle and the member 31 maintain the clutch spring centered axially between the spindles during axial clutch operating movement of 13. The compression spring 15 biases the driven spindle 13 outwardly, the nose piece serving as a stop for head 13a with the clutch mechanism disengaged.

The projecting end of the driven spindle has a bore 33 preferably of non-circular, say hexagonal, cross section to receive and bottom the shank 34 of the tool bit 14 corresponding in cross section in non-rotatable relation. The tool bit, here a screw driver bit with finder, is held removably in the driven spindle by engagement between the circumferential groove 35 in the bit shank and the detent ball 36 located in a radial aperture through the spindle wall. The ball is held from internal displacement in usual fashion by a slight constriction at the inner end of the recess, while being urged inwardly to a tool retaining position by resilient means, such as the spring ring or band 37 located within a shallow flat external circumferential groove of the driven spindle. As the latter groove with the band therein is shielded by the surrounding nose piece, the aforementioned nose piece counterbore is required to provide clearance between the band and nose piece permitting outward displacement of the band and ball in removing or replacing a bit, and to avoid damage by adventitious displacement of the band during driven spindle rotation.

The tool bit here shown is a screw driver carrying a screw finder device comprising a sleeve 40 slidable on the cylindrical tool tip portion 41 and having a bell-mouthed work end; a helical compression spring 42, disposed about the driver tip in a sleeve bore enlargement between the sleeve shoulder 43 and the collar 44 formed or fixed on the bit, to urge the sleeve outwardly beyond the driver end; and an expanding spring ring 45 in the sleeve bore groove 46 to provide a stop means in butting against the collar 44.

The driving spindle 12 is axially bored and threaded at 50 to receive therein the male threaded end of a power output shaft as often provided on power equipment or tools, or to receive as here shown a short male threaded adapter stud 51 for connection to an output shaft having female threads. The adapter shaft or stud of course may be varied in form to the requirement of the power output shaft with which the unit is used, and may have its outer end provided with an Allen wrench socket 53 for tightening or removal. A ball 52 in the recessed bottom of the spindle bore 50 may be used as a seat to position adapter studs uniformly and to take the end thrust of the shaft or adapter which is tightened into place to avoid thread damage on bottoming. A pair of wrench flats 55 on the outer end of spindle 12 also facilitates application or removal of adapter studs from the unit, or the unit itself from a powered shaft.

In use, say with an electric hand drill, the unit with suitable adapter stud is chucked in the drill chuck, or where the chuck is removable from a threaded shaft, is applied directly or by a suitable threaded adapted to the shaft, and the necessary tool bit is snapped into position in the driven spindle. The operator may grasp the housing member with one hand and the drill with the other, to direct the bit into position relative to the fastening element to be driven, and, since the spindles are rotatable relative to member 10, the operator may hold the latter 4 after the power is switched on to steady and maintain the tool position.

When the tool is positioned, force applied through the drill toward the work causes the driven spindle to slide inward against the bias of the clutch spring to bring the clutch teeth into driving engagement. Obviously with sloped clutch tooth engaging faces, the torque transmitted therethrough to overcome frictional resistance of the fastener being driven develops axially directed components additional to the spring force in tending to disengage the clutch. Since this force must be balanced by a force applied manually by the operator to maintain driving engagement, when additional driving resistance is encountered upon seating of the fastener, the clutch teeth disengage to prevent over driving and attendant disadvantages. Moreover, the fastener may be driven to a desired tightness when the operator is familiar with the working conditions by sensing and control through the manual pressure used to keep the clutch engaged.

We claim:

For a manually controlled coupling of a rotary fastener driving bit to a portable power tool having a power output shaft, a rotary fastener driver attachment device removably mountable on said shaft comprising: a generally cylindrical hollow casing with one end closed and axially bored and the other end open and counterbored, the casing exterior being adapted to one-handed grip for manually guiding and controlling of fastener driving operations; an axially bored plug pressed into the counterbore of the casing; a headed driving spindle and headed driven spindle having coaxially aligned shank portions rotatably journaled in and projecting from the bores of the casing and plug respectively with the heads thereof in opposed relation, the shank of the driving spindle including a portion threaded for removable attachment on said power output shaft as means for removably mounting the device on said tool, shank end of the driven spindle being adapted for relative non-rotational engagement with a fastener driving bit; the driven spindle shank being axially movable in the plug and the driving spindle shank including means bearing on the casing to restrain axial movement; compression spring means interposed between said spindles to urge the head of the driven spindle normally away from the driving spindle; spring guiding and centering means associated with said spring and spindles; and cooperating clutch teeth formed integrally on the opposed surfaces of said heads, said teeth each having a pair of sloping engagement faces with the slopes of corresponding tooth faces on the two heads being equal developing a disengaging force dependent upon the torque transmitted, and whereby the spindles may be brought into driving engagement for driving in either direction upon axial movement of the driven spindle and the maximum torque transmitted may be controlled by manual force applied by the operator through said tool or casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,855,456 Miller Apr. 26, 1932 1,864,844 Meunier June 28, 1932 1,913,046 Callan June 6, 1933 2,179,724 Kuehne Nov. 14, 1939 2,394,348 Wilhide Feb. 5, 1946 2,600,327 Ridge June 10, 1952 2,634,640 Pedersen Apr. 14, 1953 FOREIGN PATENTS 684,753 France Mar. 24, 1930 

